Process of producing pentaerythritol



Patented Mar. 27, 1945 F. E. Cox, Wu, Herculw Powder Company, acorporation of Delaware Application September 25, 1942,

so on This invention relates to on. improved process for the preperatlonof ntoeryt. ore particularly, it is concerned with on improved methodfor recovering pentoerythritol from the crude recstion mixture ofeceteldehyde :m-v '1 formaldehyde.

Penteerythritol has been prepared according to dlfierent proceduresdescribed in the nrt by the condensation of oceteldehyde with iormelde-=hyde in the presence oi on slimline catalyst. Consideruble oliihoultyhos been experienced in. obtaining maximum yields of nentoerythritolclue in port to the erecting conditions under which the reaction must heconducted end in port to the formation of lay-products during therecovcry of the pentoerythritol from the renction mixture. Vnriousmethods hove been desorlhed for the removal of the metal ion from thecoltolyst which is present as n ffilmttt. For example, col cium has beenprecipitated or the sulfate or ore,- lnte in such o manner thet formiccold hos reinclined in the rencticn minture. In working up thepenteerythritol-iormic acid solution, it hos been general to concentratenod cryetollire the oenteerythritol. In carrying out this concentrelion,however, non-crystollinoble syrups hove re sulted due to the formationof formic esters by reaction between the nentoerythritol end the formicacid, thus reducing the yield oi crystalline pentnerythritol.

Now, in accordance with this invention, a method has been found ofrecovering high yields of penteerythritol from. the crudepentnerythritol reaction solution resulting from the condensation ofncetnldehyole with iormelrlehyrle in the presonce of on slimlinecatalyst. The improved method involves removing formic nolol from thereection mixture by szeotronic dlstillntion with on orgonic solventimmiscible with the reaction mixture, having n hoilino point within thereuse irorn about Mr G. to ole-out 6., end which forms on szeotrone withformic ocicl Thus, in ee-rrylng out the process oi producingpentaerytluitol involving condensation oi eoetelrle hydewithionnoldehyde in the presence or en ellrollne cntehrst, followed byoclrllflcntion of the reaction minions, end removel oi the motel ion ofthe catalyst, the acidified reaction mixture is treated with on organicsolvent, immiscible therei with, having a, boiling point within therungs from shout 60 C. to shout W" (3. end which forms on nzeotrope withformic sold, and remos the nzeotrope, while the reaction mixture isbeing meintslned at or temperature of from about 60 C. to about 99 C.and preierobly from about til M, unignor to Wilmin ton, on.

' crystalline syrups.

C. to about 99 C. The immiscible solvent may be added to the reactionmixture in vapor form.

To 90 parts of formalin (35% formaldehyde) and 200 parts of weter wereodtled simultaneously ll ports ecetnldehyde end no ports calciumhydroxlde. Thereuction was corried out at a. term oernture between it"C. end tl (G. for a period six hours. After the reaction woo complete,the condensate was acidified with carbon dioride one.

filtered to remove excess lime and insoluble me.

teriel. The filtrate was then concentrated in vocuo and crystallisedalternately with removal of the crystals in crops. Alcoholwes thenwelded to the filtrate to precipitate the alcoholiusolublepentserythritol-colcium formats crystsllizoble material from theuloohol-soluble non- The penteerythritol-calcimn formste crystallinematerial amounting to to ports was removed by filtration and thendissolved in 100 parts of water and acidified with parts of sulfuricacid. The precipitated calcium sulfute was removed by filtration and wasgiven n displacement wash with water. The solution amounting to'liioports and containing pentaerythritol and formic acid was then heeted toC. while hot isobutyl chloride vapors were passed through the solution.The vnpors distilling off were condensed and collected in fractions. Thedistillate, consisting of about 775 parts oi which about 10% was water,was titrated with sodium hydroxide to determine the amount of formicacid removed, The enelysis of these fractions is tabulated below:

Weight Fraction Weight formic acid The aqueous solution thus freed offormic acid was concentrated in vacuo andv crystallized ol-' liquor byprecipitation with alcohol.

each crop of pentaerythritol being given a displacement wash with water.The last of the pentaerythritol was removed from the mother The totalyield of pentaerythritol thus obtained amounted to 28 parts by weight oran 80% yield based on the acetaldehyde.

Example 2 I To 175 parts of formalin formaldehyde) and 370 parts ofWater were added simultaneously 22 parts of acetaldehyde and 20 partscalcium hydroxide. The reaction was carried out under the same reactionconditions as in Example 1. After the reaction was complete, the

solution was acidified with 47 parts of 50% sul-- while propyl bromidevapor Was passed through the solution to carry off the formic acid as anazeotropic mixture with the propyl bromide. This was continued until1000 parts distillate containing 22 parts formic acid were collected.The propyl bromide was washed with sodium carbonate until freed or acidand was then reused in another run. The solution of pentaerythritolfreed of formic acid was then concentrated in vacuo and thepentaerythritol was crystallized. After removal of the first crop ofpentaerythritol, the solution was concentrated to get further crops. Thelast of the pentaerythritol was obtained by adding alcohol in which thepentaerythritol was insoluble and the noncrystalline syrups weresoluble. The total yield of pentaerythritol thu obtained amounted to 54parts by weight or a yield of 80% based on the acetaldehyde.

The normal formaldehyde-acetaldehyde ratio which may be used in carryingout the process of this invention may be from about 2.5 to 1 to about 6to 1 and preferably from about 4 to 1 to about 5 to '1. A preferredratio of alkaline catalyst content is from about 1.0 to'about 1.2equivalents per mol of acetaldehyde although more alkaline catalyst maybe used if desired.

In carrying out the process of this invention, calcium hydroxide ispreferred as the alkaline catalyst. However, other alkaline catalystssuch as sodium hydroxide, potassium hydroxide, barium hydroxide,magnesium hydroxide, strontium hydroxide and the like may be used.

In the examples, isobutyl chloride and propyl bromide. were shown asorganic solvents immiscible with the reaction mixture, having a boilingpoint within the range from about C.

-to about 99 C. and which form an azeotrope with formic acid. However,any other organic solvent, immiscible with the reaction mixture, havinga boiling point within the range from about 60 C. to about 99 C., andwhich will form an azeotrope with formic acid such as secondary butylchloride, ethyl iodide, benzene, trichloroethylene, and the like may beused. However, those which form azeotropes rich in formic acid as doisobutyl chloride and propyl bromide are preferred.

The temperature of the reaction mixture during the treatment with theimmiscible organic solvent may vary from about 60 C. to about 99 C. andpreferably from about 80 C. to about 99 C. The temperature will dependupon the temperature of the solvent vapors and the boiling point of theazeotrope. The treatment is crude pentaerythritol solution is shown.

continued until 90 to 100% of the formic acid has been removed, althoughif desired, it may be discontinued at any other time.

In the examples, a method of preparing the However, any other method ofcarrying out the condensation may be employed. It is preferred, however,to use a method which will direct the reaction to the formation ofpentaerythritol and keep side reactions at an absolute minimum. The timeand temperature of the reaction may vary according to known ranges. Thecondensate may be acidified with any mineral acid as sulfuric 0rhydrochloric acid by any of the means known to the art. Generally, themetal ion of the catalyst may be removed before removal of the formicacid but, if desired, the formic acid may be first removed from thecondensate. The metal ion of the catalyst may be removed in variousways. For example, if calcium hydroxide is used as the catalyst, thecalcium may be precipitated from the reaction mixture as calciumsulfate. Vapors of an organic solvent immiscible with the acidifiedreaction mixture, such as propyl bromide, which forms an azeotrope withformic acid may be passed through the reaction mixture while it is beingmaintained at a temperature of from about 60 C. to about 99 C. andpreferably from about C. to about 99 C. If desired, the solvent may beadded in liquid form to the hot solution and the vapors formed therein.The treatment is ordinarily continued until from to of the formic acidhas been removed from thereaction mixture. The reaction mixture thusfreed from formic acid may be concentrated according to the'method shownin Example 1 or any other known methods and the crystallinepentaerythritol recovered.

The formic acid may be recovered from the azeotrope by extraction withwater, or by washing with sodium carbonate, or any similar means, andthe solvent can then be re-used.

When pentaerythritol is isolated by concentration of theacidifiedcondensate of acetaldehyde in the formaldehyde, the large amounts offormic acid set free react during the concentration to esterify thepentaerythritol and to catalyze reaction between aldehydes andpentaerythritol. By the process of removing formic acid by azeotropicdistillation by means of an immiscible organic solvent which forms anazeotrope with formic acid, side reactions with pentaerythritol areprevented and a materially increased yield of pentaerythritol is thusobtained.

What I claim and desire to protect by Letters Patent is:

1. In the process of producing pentaerythritol, after condensation ofacetaldehyde with formaldehydein the presence of an alkaline catalyst,acidification of the reaction mixture, and removal of the metal ion ofthe'catalyst, the steps comprising treating the acidified reactionmixture with an organic solvent immiscible therewith, having a boilingpoint within the range of from about 60 C. to about 99 C., and whichforms a minimum boiling azeotrope with formic acid, and distilling offthe azeotrope, while said reaction mixture is being maintained at atemperature of from about 60 C. to about 99 C.

2. In the process of producing pentaerythritol,

after condensation of acetaldehyde with formaldehyde in the presence ofan alkaline catalyst,

aerator acidification of the reaction mixture, and removal of the metalion of the catalyst, the steps comdistilling ed the azeotrope, whilesaid reaction mixture is being maintained at a temperature of from about80 C. to about 99 C.

3. In the process of producing pentaerythritol, after condensation ofacetaldehyde with formal dehyde in the presence of an alkaline catalyst,acidification of the reaction mixture, and removal oi the metal ion ofthe catalyst, the steps comprising treating the acidified reactionmixture with vapors of an organic solvent immiscible therewith, having aboiling point within the range of from about 60 C. to about 99 C., andwhich forms a minimum boiling azeotrope with formic acid, and distillingoil the azeotrope, while said reaction mixture is being maintained at atemperature of form about 80 C. to about99 C.

4. In the process of producing pentaerythritol, after condensation ofacetaldehyde with formaldehyde in the presence of an alkaline catalyst,acidification of the reaction mixture, and removal of the metal ion ofthe catalyst, the steps comprising treating the acidified reactionmixture with vapors of an organic solvent immiscible therewith, having aboiling point within the range of from about 60 C. to about 99 (2., andwhich forms a minimum boiling azeotrope with formic acid, distilling oilthe azeotrope, while sa'd reac tion mixture is being maintained at atemperature of from about 80 C. to about 99 C., and recoveringpentaerythritol from thereaction mixture.

5. In the process of producing pentaerythritol, after condensation ofacetaldehyde with formaldehyde in the presence of an alkal'ne catalyst,

acidification of the reaction mixture, and removal of the metal ion ofthe catalyst, the steps comprising treating the acidified reactionmixture with isobutyl chloride to form an azeotropc with formic acid,while said reaction mixture is bein maintained at a temperature of fromabout 60 C. to about 99 C., and distilling oil the azcotropc.

6. In the process of producing pentaerythritol, aiter condensation ofacetaldehyde with formaldehyd in the presence of an alkaline catalyst,

, acidification of the reaction mixture, and removal of the metal ion ofthe catalyst, the steps com:

prising treating the acidified reaction mixture with isohutyl chlorideto form an azeotrope with formic acid, while said reaction mixture isbeing maintained at a temperature of from about 80 C. to about @9 C.,and distilling off the azeotrope.

7. In the process of producing pentaerythritol, after condensation ofacetaldehyde with formalwith inc vapor-sci hot isobutyl chloride to forman aaeotrope with formic acid, while said rtion mixture is beingmaintained at a temperature of from about d0 C to about 99 C., anddistlg oil the azeotrope.

9. In the process of producing pentaerythritol, after condensation ofacetaldehyde with formaldehyde in the presence oi an alkaline catalyst,acidification oi the reaction mixture, and removal of the metal ion ofthe catalyst, the steps com-' prising treating the acidified reactionmixture with passing vapors of hot isobutyl chloride to form anazeotrope with formic acid, while said reaction mixture i beingmaintained at a temperaturaof from about 80 C. to about 99 0.,distilling off the azeotrope, and recovering pentaerythritol from thereaction mixture.

10. Inthe process of producing pentaerythritol, after condensation ofacetaldehyde with'formale dehyde in the presence of an alkalinecatalyst. acidification of the reaction mixture, and removal of themetal ion of the catalyst, the step comprising treating the acidifiedreaction mixture with propyl bromide to form an azeotrope with formicacid, while said reaction mixture is being maintained at a temperatureof from about 60 C. to about 99 (3., and distilling off the azeotrope.

11. In the process of producing pentaerythritol, after condensation ofacetaldehyde with formaldehyde in the presence of an alkaline catalyst,acidification oi the reaction mixture, and removal of the metal ion ofthe catalyst, the steps-comprising treating the acidified reactionmixture with propyl bromide to form an azeotrope with formic acid, whilesaid reaction mixture is being maintained at a temperature of from about80 C. to about 99? C., and distilling oil? the azeotrone.

dehyde in the presence of an alkaline catalyst,

acidification of the reaction mixture, and removal or the metal ion ofthe catalyst, the steps comprising treating the acidified reactionmixture with passing vapors oi isobutyl chloride to form an azeotropewith form c acid, while said reaction mixture is being maintained at atemperature of from about 80 C. to about 99 ,C., and distilling off theazeotrope.

8. In the process of producing pentaerythritol, after condensation ofacetaldehyde with formaldehyde in the presence of an alkaline catalyst,acidification of the reaction m xture, and removal of the metal ion ofthe catalyst, the steps comprising treating the acidified reactionmixture aldehyde in 3 12. In the process of producing pentacrythritol,after condensation of acetaldehyde with formaldehyde in the presence ofan alkaline catalyst, acidification of the. reaction mixture, andremoval of the metal ion of the catalyst, the steps comprising treatingthe acidified reaction mixture with passing vapors oi propyl bromide toform an azeotrope with formic acid, while said reaction mixture is beingmaintained at a temperature of from about C. to about 99 C anddistilling old the azzeotrope.

13. In the process of producing pentaerythritol, after condensation oiacetaldehyde with formaldehyde in the presence of an alkaline catalyst,acidification of the reaction mixture, and remoral of the metal ion ofthe catalyst, the

' comprising. treating the acidified reaction bromide toform anazeotrope with formic acid,

while said reaction mixture is being maintained at a temperature of fromabout 80 C. to about 99 0., distilling ed the azeotrope, and recoveringpentaerythritol from the reaction mixture.

15. In the process of producing pentaerythritol, after condensation ofaoetaldehyde with forum the presence oi an alkaline catalyst andacidification oi the reaction mixture, the steps comprising treating theacidified reaction mixture with an organic solvent immiscible therewith,having a boiling point within the range of from about 60 C. to about 990., and which forms a minimum boiling azeotrope with formic acid, anddistillin of! the azeotrope, while said reaction mixture is beingmaintained at a temperature of from about 60 to about 99 C.

16. In the process of producing pentaerythritol, after, condensation ofacetaldehyde with formaldehyde in the presence of an alkaline catalystand acidification of the reaction mixture, the steps comprising treatingthe acidified reaction mixture with vapors of an or anic solventimmiscible therewith, having a boiling point within the range of fromabout 60 C. to about 99 C.,

and which forms a minimum boiling azeotrope with formic acid, anddistilling off the azeotrope,

while said reaction mixture is being maintained at a temperature of fromabout 80 C. to about 99 C.

1'7. In the process of producing pentaerythritol, after condensation ofacetaldehyde with formaldehyde in the presence of an alkaline catalyst,acidification of the reaction mixture, and removal of the metal ion ofth catalyst, the steps comprising treating the acidified reactionmixture with ethyl iodide to form an azeotrope with formic acid, whilesaid reaction mixture is being maintained at a temperature of from about60 C. to about 99 C., and distilling ofi the azeotrope.

18. In the process of producing pentaerythritol,

after condensation of acetaldehyde with formaldehyde in the presence ofan alkaline catalyst, acidification of the reaction mixture, and removalotthe metal ion of the catalyst, the steps comprising treating theacidified reaction mixture with ethyl iodide to form an azeotrope withformic acid, while said reaction mixture is being maintained at atemperature of from about 80 C. to about 99 C., and distilling oil theazeotrope.

19. In the process of producing pentaerythritol, after condensation ofacetaldehyde with formaldehyde in the presence of an alkaline catalyst,acidification of the reaction mixture, and removal of the metal ion ofthe catalyst, the steps comprising treating the acidified reactionmixture with passing vapors of ethyl iodide to form an azeotrope withformic acid, while said reaction mixture is being maintained at atemperature of from about 80 C. to about 99 C., and distilling of! theazeotrope.

20. In the process of producing pentaerythritol, after condensation ofacetaldehyde with formaldehyde in the presence of an alkaline catalyst,acidification of the reaction mixture, and removal of the metal ion ofthe catalyst, the steps comprising treating the acidified reactionmixture with passing vapors of hot ethyl iodide to form an azeotropewith formic acid, while said reaction mixture is being maintained at atemperature of from about 80 C. to about 99 C., and I

